Compound literals with C99

C99 allows us to use compound literal

The feature called compound literal enables us to create unnamed array and structure values

Usually, what we do in C, first we need to declare and, then initialize a variable before we call

As can be seen, from the below example

float b[]={3,0,3,4,1};
    float result = calculateSum(b,5);

But, if b isn’t needed for any other purpose then it will be a little annoying right? To create it solely for the purpose of calling  calculateSum

On the other hand, with C99 we can avoid this annoyance by using the feature called compound literal which is an unnamed array that is created simply by specifying the element it contains

float result = calculateSum((float[]){3,0,3,4,1},5);// function call

As can be seen, from the above  function call calculateSum has a compound literal ((float[]){3,0,3,4,1}) as its first argument

Let’s deconstruct an example

#include <stdio.h>
float calculateSum(float num[], float n);//function prototype declaration

int main() {
 float result = calculateSum((float[]){3,0,3,4,1},5);// function call
  printf("Result = %.2f", result);
  return 0;
}

float calculateSum(float num[], float n)//function declaration
 {
  float sum = 0.0;
  for (int i = 0; i < n; ++i) {
    sum += num[i];
  }
  return sum;
}

Output

result = 11.00